Spark plug



J. M. WATTS March 27, 1934.

SPARK PLUG Filed Jan. 25, 1932 fNI/'A/TOE: James M War/5,

HTTOENEX Patented Mar. 27, 1934 UNITED STATES PATENT OFFICE 4 Claims.

This invention relates to spark plugs, and has for an object the provision of a spark plug adapted to function under the most adverse operating conditions.

5 Particularly, the invention is adapted for use on high speed internal combustion engines.

The invention has for an object the provision of a spark plug which will function efficiently in a high compression internal combustion engine and despite general fouling thereof due to oil pumping and like adverse conditions.

The spark plug is adapted to ignite a combus tible charge in an internal combustion engine,

to the end that combustion is complete at all times, regardless of engine speed. It is well known that some engines, notably the V type, tend to roll at idling speed, whereas the vibration is usually removed as thespeed of rotation of the crank shaft of the engine increases.

It has been found by experiment that the socalled roll or vibration factor in an engine is often due to faulty ignition, particularly in the operation of the spark plugs, to the end that the combustible gas is not properly ignited in each cyl- 5 inder. It has also been found that a comparatively long spark gap should be provided for a low speed engine or an engine revolving at idling speed and a comparatively short gap at high engine speeds. The present invention presents a spark plug which is adaptable for use at all engine speeds and the electrodes are so formed as to allow the spark to jump between the electrodes at any engine speed.

The inventor is aware that spark plugs having multiple electrodes have been on the market for many years. But so far as the inventor knows, none of said electrodes have'been spaced a variable distance from some central electrode, and

- the present invention presents such a structure.

Under actual conditions and tests, the spark plug about to be described is found to function efliciently without breaking down under pressures of 140 pounds to the square inch. The spark plug has also been found to function emciently even though sprayed with oil.

The invention has for further objects the provision of a spark plug which is simple of construction, eificient in operation, and generally superior to spark plugs now on the market, so far as the inventor is aware.

With the above and other objects in view, the invention consists in the novel and useful provision, formation, construction, association, and relative arrangement of parts, members and features, all as shown in certain embodiments in the accompanying drawing, described generally, and more particularly pointed out in the claims.

In the drawing:

Figure 1 is an elevation, partly in vertical section, of one form of the improved spark plug,

Figure 2 is a bottom plan view of the spark plug shown in Figure 1,

Figure 3 is a fragmentary sectional view on the line 33 of Figure 2,

Figure 4 is a fragmentary perspective view of one of the electrodes used in practicing the invention,

Figure 5 is a fragmentary vertical sectional view of a slightly modified arrangement of the electrodes from that shown in Figure 3,

Figure 6 is a fragmentary perspective view of an electrode formed in a slightly different manner from the electrode shown in Figure 4, and,

Figure '7 is a plan view of a further modified form of electrode.

Referring now with particularity to the drawing, I have shown in Figure 1 a spark plug 1, including a shell 2 provided with external threads 3, whereby the said spark plug may be screwthreaded within the cylinder block of an internal combustion engine, with the usual porcelain insulator 4 longitudinally passed through the said shell and held to said shell through the medium of a bushing 5. This bushing is internally threaded to the said shell. A wire conductor 6 extends longitudinally of the insulator 4 carrying at 7 a terminal connection. The opposite end secures an electrode 8. It will be noted that the shell is annular in form at 9, and the said shell at the portion 9 acts as the second electrode. The electrode 8 may assume a variety of forms, several of which are shown in the remaining figures.

Referring first to Figure 4, the said electrode 8 is in the form of a disc provided with radial slits 10, thus providing the disc with segmental portions designated generally as 11. This said disc is provided with a transverse bore 12 through which the wire 6 is passed, and then headed so as to hold the said disc against the bottom of the porcelain insulator 4 as shown at 13. The said bore 12, however, is not placed at the center of the disc but is eccentric to the periphery of the disc with the result that when the disc is secured to the wire 6, as shown in Figure 1, there is a variable gap or spacing between the inner surface of the shell at 9 and the disc periphery. In Figure 1, this variable spacing is shown, and is also shown in Figure 2.

In Figure 2, the disc presents a spiral periphery in that the radius constantly changes, with the result that the radius is greatest for the segment 11, shown at 14, and shortest for the segment 11,

shown at 15. In addition to progressively varying the radius in the forms just described, I also vary the thickness of the disc, as best illustrated in Figure 3. In other words, the disc as an entirety and in cross section appears wedge-shaped. In the form of the electrode 8 shown in Figures 1 to 4, inclusive the thinnest edge portion of the disc has the nearest approach to the inner surface 9 of the shell, while the thickest portion which would be the segment shown at 15, is at the greatest distance from the shell.

In Figures 5, 6 and 7, I have reversed this order of procedure, in that the thickest portion of the disc is spaced the least distance from the shell and the thinnest portion at the greater distance. Within the purview of my invention, I do not limit it to a disc of variable thickness nor do I limit it to a disc provided with radial slots forming a plurality of segmental portions.

In Figure 7, I have provided a special periphery for a disc electrode 16, the disc being in every wise similar to the showing in the previous figures, save and except that the disc is not provided with radial slots.

The operation, uses and advantages of the invention just described are as follows:

It is easily shown that a short, thick electrical discharge occurs between thick gaps and that a relatively thin spark occurs between pointed gaps. I have made use of these principles in the present spark plug. For instance, in the form of the invention shown in Figures 4, 5 and 6, the

longest gap occurs between the thin edge of the disc and the shell, as shown at 17, and the shortest gap at the thickest portion of the disc, as shown at 18. In Figures 1 to 4, inclusive, the relationship just mentioned is reversed. In Figure '7, the thickness of the disc may be uniform or variable, in accordance with either of'the discs shown in Figures 4 and 6. For ordinary passenger cars, either form of the invention shown in Figures 3 and 5 is equally satisfactory. In any event, rolling of the motor where due to ignition is effectively overcome by the spacing of the spark plug gaps in accordance with the invention. A long gap is provided for idling speeds and a short gap for high speeds. In any event, a spark is at all times assured so far as the plug is concerned. The general instruction given is to space the spark gaps at a given maximum, and then try the motor on a pull. If the motor misses, readjust the spark gaps slightly to the point where the miss is overcome. It will be readily compression, and that no adjusting of the spark gaps is necessary as the spark plugs will function either on a pull or on a level stretch so that there is no miss in the motor. As stated, a long spark has been found best when the'motor is idling.

The average spark plug is not able to function for both high speeds and idling speeds of a motor. Consequently, an approximation is reached and the electrodes are adjusted so that the motor will not miss on a hard pull and not unduly roll on a light pull. For passenger cars, it is essential that the motor be as smooth running as possible, and the present spark plug aids essentially in smooth operation. In a measure, it is automatic as to the character of spark gap desired. The mechanic does not have to adjust or readjust the gap as it is already done for him.

In racing cars, it has been found that the flame travels completely around the periphery of the disc, at high motor speeds, with the result that a better ignit on of the combustible fuel is effected. The present spark plug, in addition to the several advantages and features heretofore outlined, has been found to be substantially carbon free after the most rigid of tests, which shows that perfect combustion is obtained by its use. While a high compression motor may use any form of spark plug gap, as illustrated, yet it has been found that the spacing shown in Figure 5 is most effective. A low compression motor will work effectively with any of the forms shown but possibly best with the form shown in Figure 3. However, I do not restrict myself to either form or forms for any particular type of motor as individual experiment will readily show which form is best adapted for a given installation.

The slots 10 allow for a ready equalization of pressures both within the shell and exterior thereof when thespark plug is functioning under operating conditions.

It is obvious that various changes and modifications and variations may be made in practicing the invention in departure from the particular showing of the drawing without departing from the true spirit of the invention.

I claim:

1. In a spark plug, a disc electrode having segmental portions of different radius and of variable thckness.

2. In a spark plug, a disc electrode having separated segmental portions, the periphery of each segmental portion differing in thickness.

3. In a spark plug, a disc electrode provided with radial slots to provide segmental portions, each segmental portion having a different radius of curvature relative to contiguous segmental portions.

4. In a spark plug, a disc electrode formed with spaced radial slots to provide segmental portions, and the periphery of said segmental portions relative to a common center for said disc having a constantly changing radius.

JAMES M. WATI'S. 

